Fasteners that allow fluid passage are often used to connect a flexible hose firmly to a rigid member having a fluid port. In one exemplary configuration, the flexible hose is connected to a fitting within an interior volume that allows fluid to flow from the interior surface of the fitting to the hose. The interior volume of the fitting is sealed with a fastener. The top opening of the fitting is sealed by the head of the fastener and the bottom opening of the fitting is sealed by the surface of the rigid member surrounding the fluid port. Fluid can flow from the fluid port of the rigid member to the interior volume of the fitting through a passage in the fastener.
Exemplary applications for such a fastener include automotive brake lines, both at the master cylinder and brake caliper; automotive clutch, oil, fuel, and cooling lines; hydraulic and pneumatic connections in industrial vehicles and equipment; gas and liquid lines in laboratory and medical equipment; and compressed air, vacuum, water, and lubrication lines in manufacturing equipment.
A common fastener used for these application is called a “banjo bolt.” A banjo bolt has an internal passage along its length that connects a port at the end of the bolt with one or more ports in the shank of the bolt. The banjo bolt requires internal axial and cross drilling to create the passage. The internal drilling can reduce the tensile strength of the fastener significantly. The drilling operation also adds expense to the production process and creates the potential for contaminants, such as metal chips and flakes, to attach to the fastener. During use, the contaminant may dislodge and cause serious damage. Metal flakes entering an automotive oil line, for example, can scratch the cylinder walls of the engine. Metal chips can also become lodged in the fluid passage and create an obstruction. An obstruction in a brake line, for example, can cause brake failure.
Another type of fastener used for fluid passage has an external linear groove along the threads. Linear grooves, however, create difficulties in the thread forming process resulting in defective thread formation and inefficient manufacturing processes. A knurl can be added to the body of the fastener to facilitate the thread forming process, however, the knurl requires an additional processing step. Additionally, the forces exerted on the knurl during the thread forming process can create metal shavings that can result in contaminants attaching to the fastener.
A need exists for alternative fluid passage fasteners that can be produced in a cost effective manner for use with existing fittings designed for banjo bolts. The fluid passage fastener should be manufactured using processes that minimize the potential for creating contaminants that can attach to the fastener.